Automatic firearms fed with cartridges by means of flexible belts, especially for use on aircraft



y 1956 B. MAILLARD 2,756,638

AUTOMATIC FIREARMS FED WITH CARTRIDGES BY MEANS OF FLEXIBLE BELTS,ESPECIALLY FOR USE ON AIRCRAFT Filed July 3, 1952 2 Sheets-Sheet l l l Il l I I l I 0 I l I l I I l I I mild R Em 70 y 31, 1956 B. MAILLARD2,756,638

AUTQMATIC FIREARMS FED WITH CARTRIDGES BY MEANS OF FLEXIBLE BELTS,ESPECIALLY FOR USE ON AIRCRAFT Filed July 3, 1952 2 Sheets-Sheet 2 i 20J] F a I; 15 /]5 15 z 6 INVE'IVTOR 2% R QM ATTORNEY llnited StatesPatent @fiice 2,756,638 Patented July 31, 1956 AUTOMATIC FIREARMS FEDWITH CARTRIDGES BY lVIEANS F FLEXIBLE BELTS, ESPECIALLY FOR USE ONAIRCRAFT Bernard Maillard, Geneva, Switzerland, assignor to SocietyBrevets Aero-Mecaniques, S. A., Geneva, Switzerland, a society ofSwitzerland Application July 3, 1952, Serial No. 297,058 Claimspriority, application Luxembourg July 10, 1951 6 Claims. (Cl. 89-335)The present invention relates to automatic firearms fed with cartridgesassembled to form flexible belts actuated by a feed mechanism working insynchronism with the arm. In the following specification and claims, theexpression automatic firearm will be used to designate not only the armproper but also the feed mechanism for actuating the cartridge belt.

The chief object of my invention is to provide a firearm of this kindwhich is better adapted to meet the requirements of practice than thoseused up to the present time and in particular which can work at higherrates of firing.

My invention is concerned with automatic firearms including, for thefeed of the cartridge belt, two elements, to wit a belt feed mechanismimparting a jerky movement to the end of the belt close to the breechmechanism and auxiliary driving means, located upstream of the firstmentioned one, tending to give the belt a more regular feeddisplacement, advantageously at constant speed. My invention ischaracterized in that there is further provided, for guiding thecartridge belt between the auxiliary driving means and the belt feedmechanism, a rigid passage, preferably rectilinear and in line with theinlet passage of the firearm proper, the section of this passage beingof a height sufiicient to enable the belt to fold in zigzag fashion insaid passage, the cartridges assuming a staggered disposition therein.

A preferred embodiment of the present invention will be hereinafterdescribed with reference to the accompanying drawings, given merely byway of example, and in which:

Fig. 1 is an end view, partly in section on the line II of Fig. 2, of anautomatic firearm according to my invention.

Fig. 2 is a plan view corresponding to Fig. 1.

Fig. 3 is a sectional view on the line IIIIII of Fig. 1.

Fig. 4 is a side view corresponding to Fig. 3.

My invention is concerned with firearms to which the cartridges C aresupplied in the form of flexible belts formed for instance by links Massembled together by the cartridges which constitute hinge pins forthese links.

The firearm proper A may be of any suitable construction, for instanceof the open breech type, this arm being preferably mounted slidable in acradle B (rigid with the aircraft structure), with the interposition ofan elastic returnsystem (not visible in the drawing).

The system for supplying cartridges successively to the firearm properincludes, in the conventional manner, a belt feed mechanism P exerting adiscontinuous pulling action on the end of said belt close to arm A,this belt feed mechanism being advantageously mounted rigid on cradle B.

It should be noted that belt feed mechanism P may be of any typewhatever suitable for feeding cartridges to arm A, for instance of thesliding piece type or of the rotor type, and that it may receive theenergy necessary for actuating the cartridge belt either from a sourceex- ,ternal to the firearm or from a moving part of said firearm, thisenergy being for instance supplied by a portion of the kinetic energy ofarm A during its recoil stroke with respect to cradle B.

Such a system, if used alone, has, for relatively great cartridgecalibers and for high firing rates, the following drawbacks:

The discontinuous pulling action exerted on the cartridge belt by beltfeed mechanism P produces positive and negative accelerations of saidbelt which are the more important as the caliber of the cartridges isgreater and the firing rate higher.

Now this quick succession of accelerations tends to create, in thecartridge belt, in particular due to the elasticity of links M and tothe inertia of cartridges C, undulatory movements which may, in certaincases, start from the very inlet of the belt feed mechanism and arealways detrimental of a good feed of the cartridge belt toward said beltfeed mechanism.

The existence of this phenomenon limits the caliber and the rate offiring of automatic firearms fed by means of flexible cartridge belts.

It has already been proposed to limit the development of the disturbingwaves to a relatively small portion of the cartridge belt.

For instance, for this purpose, the auxiliary belt driving means,working at constant speed, has been connected to the belt feed mechanismthrough a conduit of variable length formed by a telescopic assembly ofelements, the perturbing Waves being then limited to the portion of thecartridge belt that is circulating through this conduit, the variationsof length of which allow for a gradual damping of said waves.

However, this construction had the disadvantage of introducing betweenthe auxiliary belt driving means and the belt feed mechanism adeformable guiding element the operation of which may be perturbed whenhigh external accelerations occur, which is the case with a firearmmounted on a fighting aircraft.

According to my invention, in order to avoid this drawback, I connectthe outlet of the auxiliary belt driving means with the inlet of thebelt feed mechanism by a rigid passage or conduit 1, preferablyrectilinear, the

vertical section of which is sufficient to enable the belt to fold inzigzag fashion so that cartridges C assume a staggered dispositioninside this conduit, the height h of this conduit being for instanceabout twice the thickness of the belt.

As the section afforded to the belt at the outlet of the auxiliarydriving means and at the inlet of the belt feed mechanism is of a heightcorresponding to the thickness of the belt, rigid conduit 1 isadvantageously joined to said auxiliary driving means outlet and beltfeed mechanism inlet through oblique wall elements 1a.

Furthermore, the system is preferably arranged in such manner that themaximum increase of length of the zigzag folded portion of the belt(which increase is due to a flattening of this zigzag portion) is atleast equal to the length of the sudden displacement imparted to thefirst cartridge of the belt to engage it into the firearm proper, everytime a shot is to be fired.

In other words, rigid passage 1 is so arranged, account being taken ofthe diameter of the cartridges and of the interval between them, that,the cartridge located at the inlet of said passage being supposed to bestationary, it is possible to give the cartridge located at the outletend of said passage a displacement of the above mentioned length.

This condition is complied with by suitably choosing the height h ofconduit 1 and/or the length thereof.

On the other hand, it is advisable not to exceed, for height h, themaximum value compatible with a regular zigzag folded arrangement of theportion of the belt that is being considered, that is to say with anarrangement such that, for the maximum folding of this belt portion, thesuccessive cartridges thereof are bearing alternately against the topand bottom walls of passage 1. Advantageously, these top and bottomwalls are provided with projections b extending parallel to the axes ofthe cartridges and intended to facilitate the correct staggeredarrangement of said cartridges. It can be seen that the projectionsrestrict the distance between the top and bottom walls of the passage soas to prevent the displacement of the cartridges from the normal orderor sequential arrangement thereof. That is to say, the distance betweenthe top and bottom walls of the passage is such that one cartridgecannot pass another cartridge.

With such a construction, only the portion of the belt located in rigidpassage 1 will be influenced by the impulses imparted by the belt feedmechanism P.

Furthermore, the relatively loose guiding of this portion of the beltwill achieve a damping of the oscillatory effects resulting from theoperation of belt feed mechanism P.

Preferably, the auxiliary belt driving means are operated by the energysupplied by the recoil of thefirearm proper A with respect to its cradleB.

In the construction illustrated by the drawing, the rigid passage orconduit 1 is carried by the belt feed mechanism P and the actuatingelements of the auxiliary belt driving means are constituted by a pairof sprocket wheels 2 keyed on a shaft 3 journalled in two side plates inline with the side walls of passage 1, upstream of said side walls. Sideplates 1b carry grooves 4a and 4b respectively, for the guiding of thecartridges (these grooves cooperating respectively with the rear end ofthe cartridge case and the point of the shells).

A drum 5 journalled on shaft 3 contains a spiral spring 6 the inner endof which is secured to said shaft 3 and the outer end of which issecured to said drum.

A ratchet wheel 7 rigid with said drum cooperates with a holding pawl 8arranged in such manner that drum 5 can rotate only in the directioncorresponding to the displacement, through driving wheels 2, of thecartridge belt toward passage 1.

Ratchet wheel 7 is driven in this direction (indicated by an arrow F) byan oscillating lever 9 pivoting about the axis of shaft 3 and carrying aratchet arm 10 elastically held in active position by a spring 11, saidratchet arm 10 being arranged to work in the same direction as holdingpawl 8, that is to say so as to drive ratchet wheel 7 and drum 5 in thedirection of arrow F.

Oscillating lever 9 is actuated by a connecting rod 12 one end of whichis pivotally connected to said oscillating lever, for instance about theaxis 13 of ratchet arm 10 and the other end of which is pivotallyconnected to one arm of a lever 14 pivoted at 15 to the frame whichcarries rigid conduit 1. The other arm of lever 14 is held by a spring16 in contact with a control cam 17 rigid with the firearm proper A.

The operation of this firearm is as follows:

The arm being ready for firing and spiral spring 6 partly tensioned, thecartridges of the belt fill passage 1, where they are packed instaggered arrangement, the cartridge located in the vertical plane ofshaft 3 being engaged in one notch of each of the driving sprockets 2.As soon as the first shot has been fired, the belt feed mechanism P isactuated by the recoil of the firearm and suddenly pulls in the firstcartridge C1, producing a simultaneous displacement toward the firearmproper of the cartridges C2, C3, etc. present in passage 1. Due to therecoil of the firearm, cam 17 causes lever 14 to pivot and to drive,through connecting rod 12, ratchet wheel 7 in the direction of arrow F.This wheel in turn drives drum 5 which tensions spiral spring 6 a littlemore. This increased tensioning of spring 6 has for its effect to driveshaft 3 and wheels 2 which cooperate with the belt to introduce intorigid passage 1 a new cartridge the presence of which restores thecartridges in said passage to their initial staggered arrangement.

It should be noted that, initially, a certain time will elapse beforethe whole of the belt is driven at constant speed. During this period,for which the tensioning of spiral spring 6 goes increasing on everyshot that is being fired, the belt feed mechanism P can always draw frompassage 1 the cartridge necessary for feeding the firearm A. The onlyconsequence of the particular conditions during this starting periodwill be that the pack of cartridges present in staggered arrangement inpassage 1 will be somewhat loosened. When firing is stopped, the beltfeed mechanism immediately stops catching cartridges from passage 1 and,under the effect of the residual tension of spring 6 and of the inertiaof the belt, driving sprockets 2 will keep rotating for a short time,thus feeding the belt toward passage 1 and stopping only when thispassage is again packed.

In a general manner, while I have, in the above description, disclosedwhat I deem to be practical and eificient embodiments of my invention,it should be well understood that I do not wish to be limited thereto asthere might be changes made in the arrangement, disposition and form ofthe parts without departing from the principle of the present inventionas comprehended within the scope of the accompanying claims.

What I claim is:

1. An automatic firearm of the kind in which the cartridges areassembled in the form of a flexible belt which comprises, incombination, a belt feed mechanism for imparting, every time a shot isfired, a jerky movement toward the firearm to the end of the belt closeto said firearm, auxiliary belt driving means for imparting a moreregular movement in the same direction and at the same rate to a portionof the belt located at a distance from said end thereof, and a rigidpassage between said driving means and said mechanism, and the distancebetween the top and bottom walls of the passage being greater than thethickness of the belt and being restricted so as to prevent thedisplacement of the cartridges from the sequential arrangement thereofwhereby said belt can be packed in zigzag fashion in said passage sothat the cartridges are in staggered arrangement therein, the height andlength of said rigid passage being such that the difference between thelength of belt folded in zigzag fashion in said passage and the lengthof said passage is at least equal to the length of the suddendisplacement imparted by the belt feed mechanism to the first cartridgeof the belt to engage it into the firearm proper every time a shot isfired.

2. An automatic firearm according to claim 1 in which the top and bottomwalls of the rigid passage are provided with projections in the form ofcylindrical sectors having their generatrices parallel to the axes ofthe cartridges, to facilitate the positioning of the cartridges instaggered arrangement in said rigid passage.

3. An automatic firearm according to claim 1 further includingconvergent parts to connect the rigid passage to the belt feed mechanismand to the auxiliary belt driving means, said auxiliary belt drivingmeans and belt feed mechanism being arranged to guide the belt in theform of a substantially flat band.

4. An automatic firearm according to claim 1 in which the rigid passageis carried by the belt feed mechanism.

5. An automatic firearm according to claim 1 including a cradle, afirearm proper adapted to recoil with respect to said cradle, and meansoperative by the kinetic energy. of the firearm during its recoilmovement for actuating said auxiliary belt driving means.

6. An automatic firearm of the kind in which the cartridges areassembled in the form of a flexible belt which comprises, incombination, a belt feed mechanism for imparting, every time a shot isfired, a jerky movement toward the firearm to the end of the belt closeto said firearm, auxiliary belt driving means for imparting a moreregular movement in the same direction and at the same rate to a portionof the belt located at a distance from said end thereof, and a rigidpassage between said driving means and said mechanism, the distancebetween the top and bottom walls of the passage being greater than thethickness of the belt and being restricted so as to prevent thedisplacement of the cartridges from the sequential arrangement thereofand over most of its length smaller than twice the thickness of saidbelt whereby said belt can be packed in zigzag fashion in said pas sageso that the cartridges are in staggered arrangement therein, theauxiliary driving means including a shaft parallel to the line of fireof said firearm, two sprocket wheels adapted to engage the cartridges ofthe belt, keyed on said shaft, a drum journalled on one of the ends ofthe shaft, a spiral spring in said drum having its inner end secured tosaid shaft and its outer end secured to said drum, a ratchet wheel rigidwith said drum, pawl means for allowing said drum to rotate only in thedirection for which said sprocket wheels drive the cartridge belt towardsaid rigid passage, an oscillating lever rigid References Cited in thefile of this patent UNITED STATES PATENTS 2,379,451 Nelson July 3, 19452,383,830 Trotter Aug. 28, 1945 2,405,207 Green Aug. 6, 1946 2,415,413Burgess Feb. 11, 1947 2,479,633 MacKenzie Aug. 23, 1949 FOREIGN PATENTS607,840 Great Britain Sept. 6, 1948

